Vulcanizable chlorosulfonated polymers



accordance with the present invention.

i ate'nteci Feb. 19, 1 952 VULCANIZABLE CHLORO SULFONATED POLYMERS Ambrose McAlevy, Wilmington, Del., assignor to I. du 'Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application May 19, 1947,

Serial No. 749,100

' 4 Claims.

. 1 This invention relates to chlorosulfonated polymers and more particularly to certain novel uncured chlorosulfonated ethylene polymers in which the chlorine and sulfur contents are such that the said product has the properties of a high-quality synthetic rubber.

A process for preparing chlorosulfonated hydrocarbon polymers has been disclosed in the McQueen U. S. Patent 2,212,786 (cf. also Br. 542,414). According to the said process chlorine and sulfur dioxide are reacted simultaneously with olefin polymers; the resulting products contain combined chlorine, and also combined sulfur in the form of sulfonyl chloride groups. The patent states that satisfactory results were obtained by using from 1 to as high as to mols of sulfur dioxide per mol of chlorine, amounts of 3 to 6 mols of sulfur dioxide per mol of chlorine being preferred. In one of the embodiments (Example 2 of U. S. 2,212,786) polythene was employed as the olefin polymer and the sulfonyl chloride product obtained analyzed 3.8%

sulfur and 18.8% chlorine. The chlorosulfonated polythene thus obtained was not rubber-like, and therefore differed in kind from the chlorosulfonated polythenes which are prepared in The chlorosulfonated polymers of U. S. 2,212,786 are described as being useful in making tanning agents for leather, and applicable as fat liquoring agents, i. e. they had sufiiciently high sulfur content to impart a surface-activating efiecti There is no disclosure in the said patent of the of 'normally solid ethylene polymers, normally solid ethylene/vinyl chloride interpolymers and normally solid ethylene/vinylidene chloride interpolymers, and the like, provided the chlorine content of the resulting polymer is within the range of about to 37%, the peak in rubber-like properties being within the range of 27 to 30%,

and the sulfur content is within the range of 0.4 to 3.0%, with an optimum in curing properties at about 1.3 to 2.3% sulfur.

The rubbery chlorosulfonated polymers obtained in accordance with this invention contain polysulfonyl chloride groups. These chlorosulfonated polymers may be prepared by any suitable method such as by reacting the parent polymer with (1) C12+SO2, (2) SOzClz, or (3) SO2C12+C12; by chlorinating the parent polymer and thereafter introducing the sulfonyl group by SO2+CI2, SO2C12, SO2C12+C12, etc. The introduction of chlorine and sulfonyl chloride groups may be accomplished in two or more stages if desired, e. g. the material treated in the final stage of the chlorosulfonation may be chloropolythene, or a chlorosulfonated polythene which is too low in sulfur content and/or chlorine content. Generally, but not invariably, the chlorosulfonation reaction is carried out in the presence of an inert organic liquid such as carbon tetrachloride. Artificial radiation may be employed to increase the efficiency of the chlorosulfonation reaction. Alternatively, the reaction may be conducted in the dark, and organic peroxides or 1 other free radical producing substances may be rubbery form of chlorosulfonated polythene, or-

of chlorosulfonated polythene having a sufficiently low sulfur content to be of value as a vulcanizable elastomer. Thus, while the chlorosulfonated hydrocarbon polymers are broadly disclosed in the said patent, the specific new kind of chlorosulfonated polythene which is useful in the manufacture of synthetic rubbery materials is not suggested by the said broad disclosure. 'An object of this invention is to provide an uncured, i. e. unvulcanized, synthetic rubbery product capable of being converted to a vu1can ized rubbery material which does not have the undesirable characteristics of cured natural rubber (e. g. unsatisfactory aging properties, etc.). Other objects of the invention will appear hereinafter.

.It has been discovered in accordance with this the weight of chlorine reacting, which is com ed polymers can be prepared by chlorosulfonation paratively easy to measure. Control over the sulfur content of the product is somewhat more dimcult, but, when Cl2+SO2 are employed as reactants, it can be achieved fairly well by employing an appropriate quantity of S02 and carrying out the reaction with $02 at a temperature below about C., after some of the chlorine has already reacted. This results in a high percentage utilization of the S02 and thus permits fairly accurate control over the sulfur content of the product. In isolating the chlorosulfonated polymers from the reaction mixtures, it is generally desirable to remove the organic solvent (when one is used) by steam distillation and this may cause a partial hydrolysis of the sulfonyl chloride groups to sulfonic acid groups. This hydrolysis, if it occurs, has no substantial efiect upon the vulcanizability of the chlorosulfonated polymers.

The chlorine content of the chlorosulfonated polymers determines the rubbery, i. e. elastic. properties to a very considerable extent. Chlorosulfonated polythene having a chlorine content below about is somewhat wag y, and is tacky when warmed. Thechlorosulfonated.polythenes having relatively low chlorine contents closely resemble polythene itself. Within the range of about 20% to 45%, the chlorosulfonated polythenes are not wax-like, but., have; a rubbery character. This is especially true of the chlorosulfonated polymers having abput tq 37% chlorine, the latter rubbery-pr ducts being free of the stiffness which character zesthe chlorosulfonated polymers of higher chlorine content.

At chlorine contents above the -chlorosulfonated polythenes are very stiff, and at relatively higher chlorine contents they are virtually inflexible and glass-like.

The sulfur I content ot the p .c hlorosulfonated polythenes is highly critical, and; must be within a comparatively narrow range it. satisfactory vulcanizable rubber-likeiproducts are to be obtained. Chlorosulfonated polythenes having a sulfur co tent below 0.4 are substantially. unvulcaniz able in the absence of an a'gent ior introducingn w reactive centers. The chlorosulionated polythenes having a sulfur content above about 3% do not yield satisfactory vulcanizates because, upon heating to curin'g temperatures, they overcure, i. e. yield products which are either sub stantially inflexible orare ,mnch. less extensible and much less flexible than therubber-lilre products obtained from the .chlorosulfonated polythenes having less than about, 3%, of combined sulfur. Within the 0.4 to 3.0% range the force required to stretchthe curedpolymer to; a fixed percentage (e. g- 300%) .yaries almost linearly with the sulfur. content. This; permits themanufacture of tailor-made elastomers having predetermined elastic moduli. I

The effects of changing thechlorine and sulfur contents of chlorosulfonated polythene H are recorded in the following tables.. .The chlorosulfonated polythenesfllisted in Tables I andII were prepared by substantially theisameprocedure as is described in detail in Example; 1, except that the quantity of chlorine and sulfur diogride charged in eachinstance was sui icientto produce the stated contents of chlorine and sulfur.

TABLE I I Change in p o s. 9!. c en iqi hsf'i fnate'd polythene with variation in chlorine content Chlorine Sulfur Expt.

No. Content Content ..B W

1. 17.0 1. 54 Stiff, somewhat waxy. 2. 18.0 1. 11 Still, somewhat waxy; cured product colddraws. 3. 18. 7 1. 04 Stiff, somewhat waxy; cured product cold draws. 1 4. l9. 4 1.27 Stiff, somewhat waxy cured product cold draws.

5.. 20.0 1. 51 Stretches, but-tears easily; fairreccvery after stretch; cured product cold draws.

6. 23.8 1. 16 Rubbery.

7. 24. 6 1. 66 Rubberlike.

10.... 36.3 1.50 D0 v r 11. 40. l 2. 72 Stiff, somewhat rubbery.

l4. 51. 4 1. 4 Nearly innerible, glassy plastic.

4 TABLE II C'hwnge in properties of chlorosulfonated pol w thene with variation in sulfur content Expt. Chlorine Sulfur No. Content Content Remarks l5. 28. 6 0.12 Rubberlike, but fails to cure. 16. 34. 4 0. 31 '1' ;D0.; v 17.-.. .34..9 .0. 4 Rubberlike partially cures. 18. 34. 0 0.72 Rubberlike, cures satisfactorily. 19. 35. 5 1. 16 Do. '20- 35.7 1.4 Do. 21-. 35.7 1.63 Do. .22. 38.3; -1. 77 Do. '23.... 3219 2.0 Do. 24. 35. l 2. 32 Do. 25. 33. 4 2. 45 Do. 26. 25.. 9 2. v(i5, Do.

27. ;39. 4 2.86 Rubberlike, stiff, cures satisfactorily. '28. 36.3 2192 Rubberlike, cures satisfactorily. 29. 33.6 3 21 Rubberlike, overcurcs. '30. 32. 9 4. 23 D0. 31. 30:2 5. 12 Do. 32. 25. 6 8. 96 Do.

1 The curing test was made by heating the chlorcsulfoneted polymer in a mold with one part Agerite Alba (a trade name for hydroquinone monobenzyl ether), 1, part Captax, (mercaptohcnzothiazole) 10 parts wood rosin, 40 parts litharge at 120-l40 C. for to minutes.

An explanation for the i'ste'neeofa c "tidal range of sulfur content in the ,vulcanizable chlorosulfonated polythene'scan .be found 'byconsidering the efiect of 'the' sulfur contnt on the percentage of moleculesjhavi'fig noorionl'y'o'iiereactive group. If theyariation 'oi percent uni fulc'aniaables i. e. molecules havingjnoorbnlyione reactive group (-SOaQl}. asdeterinmmed by' he percent sulfur for "chlor'osulfonated polythenes containing30 Clfi's calcula d ,the tollowin' results'are obtained. The ca lc'ulatiohs'are based upon a polythene molecular weight of l'2',000fp:rior to chlorosulfonation, butjsirnilar'resiilts areobtained when the calculation. is'base'd 'iiponfio'lythene molecular weights "considerably higher than 12,000. H W

TABLE III Efiect of per cents .on, the percentdge'of molecules ha'bi'rig hd'or nl We ct v yf w 'ifer iinn Per cent S (for Unvulcangg g g g chloropolythene jfifig g i g izablejld. e. i y d b containiug,30% Molecules i g y '01. activated fi g g igfig having'n'o; or 2 by SO:C1) p Y only onercj i es gep i 0. 0 0. 0 0. 0 11cc 0. 23 0; l6 1. 0 75 0. 4.6 0.32 2. 0 5.40 0. 69 O. 48 3. 0 .20 O. 91 0. 64 4'. O 10 1. 14 0. 5, 0 4 1. 60 1% I 7. 1

p This table. providesatie stiape na tion for the: fact that pronouncedichangos a nature of the cured product: resmmmm' 'sinall hange in su fur cents-intend h at sulfur contntsb'eld .047 amounts of unyulcafnizablefl I Thus at a sulfurcont'entof'02 K V of the molecules are fvu1can1zable, 1w I sulfur content of 0.69%1on1yreiativm jfe ill cules remain funvulcani'zablefl[Itialso that at sulfur. contentswliichia e so overcur'ing cannot be avoided 'the'num active'igroups' per molecule'jisso'iicsslve. result Substantially "in immobility bf the resin molecules. l

4 fl'he' molecular weight of the. polymer jpfiori to introducing the substitiintgroups'shoiild' be at least 10,000. Lower molecular weight polymers give soft, sticky, non-rubbery chlorosulfonated products which are not of the kind involved in the present invention. Polymers having molecular weights of about 10,000 to 25,000 are usually employed, but polymers having much higher molecular weights also may be used.

Methods for curing the chlorosulfonated polymers of this invention are described in detail in U. S. Patents 2,416,060 and 2,416,061.

rubbery uncured chlorosulfonated ethylene/vinyl chloride and ethylene/vinylidene chloride interpolymers are included in the compositions contemplated by the present invention. The abovementioned polymers, prior to chlorosulfonation, are, in general, soluble in toluene at the boiling point (111C).

The preparation of rubber-like vulcanizable ohlorosulfonated polymers of the invention is illustrated further by mean of the following examples.

Example 1.Into a glass-lined reaction vessel equipped with a stirrer, an inlet tube under the stirrer, a reflux condenser, Pyrex windows for the admission of radiation from a type H4 lamp and a 300 watt tungsten filament lamp, and a jacket for the introduction of either steam or cold water, wa introduced 97.3 pounds of carbon tetrachloride and 2.2 pounds of polythene having a molecular weight of about 12,000-18,000. Steam was injected into the jacket causing the carbon tetrachloride to boil. During the boiling of the carbon tetrachloride the mixture was stirred, and carbon dioxide was introduced through the inlet tube until all of the air in the system had been displaced. The lamps were then turned on and chlorine was introduced through the inlet tube. The temperature of the mixture at this stage was 77 C. The injection of steam was stopped, and the exothermic heat of the chlorination was removed by injection of cold water into the jacket. After 45 minutes the temperature of the chlorination mixture had dropped to 56 C. Sulfur dioxide was then introduced, while continuing the introduction of chlorine. This was continued for 95 minutes, the lowest temperature reached being 43 C. The introduction of sulfur dioxide was then stopped, but the introduction of chlorine was continued for 30 minutes more at a temperature of 53 to 70 C. The total weight of chlorine introduced was 2.0 pounds, and of sulfur dioxide, 0.117 pound. During the entire chlorination the exit gases were,scrubbed with carbon tetrachloride, and the scrubber eilluent was passed continuously into the chlorinator. The chlorosulfonated polythene in the product was recovered by injecting steam into the inlet tube and distilling over the carbon tetrachloride. The recovered wet resin was washed thoroughly with water and dried on a rubber mill. It closely resembled natural rubber in general appearance. It had a chlorine content of 30.0 and a sulfur content of 1.6%. The percentage utilization of the chlorine was 98.1% and of the sulfur dioxide, 88.2%. Similar results are obtained when the experiment is repeated using, in place of polythene, a high molecular weight polymethylene prepared in accordance with U. S. 2,352,328.

Example 2.-A solution containing parts ethylene polymer, which has a molecular Weight of 20,000-25,000, and 670 parts carbon tetrachloride is stirred rapidly at the boiling point of the solvent while 24.9 parts chlorine and 6.7 parts sulfur dioxide are bubbled into the mixture. A type H4 mercury vapor lamp is used to irradiate the reactants. After 21 minutes, during which time the temperature is allowed to drop to 40 0., the reaction-is complete. Removal of the "solvent isaccomplished by steam distillation, following which the rubbery residue is washed with water to remove water-soluble acids. The polymer, after drying contained 27.6% chlorine and 2.76% sulfur.

Example 3.'One hundred twenty-five grams of chlorosulfonated polythene having a chlorine content of 34.9% and a sulfur content of 0.4% is dissolved in 2.5 liters of carbon tetrachloride, and the mixture is heated with grams of SO2C12 for 120 minutes at 76 C. The product is freed of solvent and soluble acid by the action of steam, and the resulting rubber-like resin is dried on a rubber mill. It has a chlorine content of 34:0-% and a sulfur content of 0.72%.

Example 4.-Twenty-five parts of an ethylene polymer having a molecular weight of 12,000- 15,000 is dissolved in 800 parts of carbon tetrachloride in a Pyrex vessel at 77 C. To the solution is added 15 grams sulfuryl chloride (1. e., sulfuric oxychloride) and the mixture is stirred rapidly while being irradiated by means of a 300-watt tungsten filament incandescent lamp. Under these reaction conditions 30 grams of chlorine and 13 grams of sulfur dioxide are introduced over a period of one hour. The resinous product is then precipitated by adding a large excess of methanol, and the precipitate is washed several times with methanol. Finally the product is freed'of volatile matter by drying in a vacuum oven at 50 C. This gives a rather stiff rubbery resin which contains 37.3% chlorine and 1.0% sulfur.

Example 5.A solution containing 25 parts of a vinyl chloride-ethylene copolymer (chlorine content, 20%; molecularweight, 20,000-22,000) in 1200 parts of boiling carbon tetrachloride is treated with 15 parts of chlorine and 7 parts of sulfur dioxide under radiation from a 300-watt tungsten filament lamp. The product is precipitated by addition of methanol. After drying in a vacuum oven, it is found to contain 32.0% chlorine and 1.26% sulfur. A similar result is obtained by subjecting an ethylene/vinylidene chloride copolymer (chlorine content, 20%) to the same reaction conditions.

It is to be understood that any convenient method for vulcanizing the chlorosulfonated polymers of this invention may be employed, and that vulcanization methods other than those described in U. S. Patents 2,416,060 and. 2,416,061 are effective in the preparation of cured elastomers from the products of the present invention. It has been discovered for example that these products may be cured by milling with certain inorganic salts such as salts of chromium, iron, zinc, etc. Moreover, it has also been discovered that curing of these products can be effected by the use of heat alone in the absence of catalysts or other c'iiring aids Furthermore,

S iifi d i g 9 1 39 1, Iof. ID-l "strain, s; 579,317," fi1ed"F'ebr a122," 1945,

esame-t, H, i It is to be finder'stood 'thatfth'e: chlo'ro'snlfonalted polymers of "the firesnt" iifve'n'tiori nta'iri substitiientgroups along the" polymer cf chainfand that the p'resent'i'nventioii is not'conceiiied with the said snbstitiited fiolyxiirs; Chlorinolysisbf the bolynierhhaififto low molecular weight s'n bstances is"not "encoiifitered'inthe' practicebf the present ti'on.

Theterm f i ytfiene,""as""nijifoyed' herein,

" fineans those substantiall linear payee; -'of ethylene 'wnicnareper'se suitableioriise m plas- "tics (Inclf Eng'. che 37f, "596fB'r tisiYPstent "Since many different embodiments (pf-"this" invention may be made withouthpartingEfrem forth in the appended claims.

I claim: V v H 1. A rubber like, "fiiiciired chlbiosulionatecl polymer of the class' consisting of ho'r'man' solid ethylene poly'r'nerj riaimany solidinoly'rnethylenes, normally 'solid ethylene/yinyl' chloride 'ihterpolw "triers, and normally solid thylne/vinylidene chloride inter-polymers, said chlors ilfona'ted poly I then having a'fchlorine content o fabout 25% chlorosulfonation b'mg'sbmm in toluene at 1 1 1 8 G and having a molecular weight in excess of 10;000.

2: Rubber-like, uncured chlorosu1fonated-nor ""'mally" solid ethylene polymer having a chlorine content'of 25% to 37% by'weight and a sulfur c'ontent of 1.3 to 2.3% by Weight" said ethylene polymer priorto chlorosulfonation'having a molecular Weight in excess of 10,000.

3. Rubber-like, uncured chlorosiilfonated ethylene/vinyl chloride interpolymer having a chlorine content of '25 to 37% by weight and a sulfur content of 0.4 to 3.0% by 'weight saicl -ethylene polymer prior to chlorosulfonation hav- --ing a molecular Weight in excess of 10,000.

ii 4. A" rubber-like uncuredchlorosulfonated-normally' solid ethylene/polymer having a-chlorine content of 27 to 30% by weight and a sulfur content of 1.3 to 2.3% by weightsaidethylene "polymer prior to chlorsulfonation -havinga *"molcula'r' weight in excess of 10,000.

AMBROSE MCALEVY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

1. A RUBBER-LIKE, UNCURED CHLOROSULFONATED POLYMER OF THE CLASS CONSISTING OF NORMALLY SOLID ETHYLENE POLYMER, NORMALLY SOLID POLYMETHYLENES, NORMALLY SOLID ETHYLENE-VINYL CHLORIDE INTERPOLYMERS, AND NORMALLY SOLID ETHYLENE-VINYLIDENE CHLORIDE INTERPOLYMERS, SAID CHLORSULFONATED POLYMER HAVING A CHLORINE CONTENT OF ABOUT 25% TO ABOUT 37% BY WEIGHT AND A SULFUR CONTENT OF 0.4 TO 3.0% BY WEIGHT, SAID POLYMER PRIOR TO CHLOROSULFONATION BEING SOLUBLE IN TOLUENE AT 111* C. AND HAVING A MOLECULAR WEIGHT IN EXCESS OF 10,000. 